BRIEF REPORTS

Dysembrioplastic Neuroepithelial
Tumor:
Cytological Diagnosis by Intraoperative
Smear Preparation
Luiz F. Bleggi-Torres, M.D., Ph.D., M.I.A.C.,1,2*
Mário Rodrigues Montemór Netto, M.D.,1
Emerson Leandro Gasparetto, M.D.,1 Adriano Gonçalves e Silva, B.M.,1
and Marlus Moro, M.D.3

The dysembrioplastic neuroepithelial tumor (DNT) is a benign and
slow-growing temporal lobe cortical lesion that presents with
clinically unresponsive partial and complex seizures, with onset
before age 20 yr. DNT shows a multinodular architecture and the
presence of mixed glioneural elements. The authors report on a
case of DNT diagnosed by the intraoperative smear cytological
technique. We describe the cytological characteristics of smear
preparations of DNT, with emphasis on the differential diagnosis.
The authors present a 5-yr-old male with partial seizures for the
preceding 3 yr. The patient showed no other neurological deficits.
Magnetic resonance identified a lesion in the cortical area of the
right temporal lobe. The smear cytology showed small, round,
oligodendroglial-like cells arranged in lobules, with microcystic
spaces containing ganglion cells floating in a fine fibrillary background. Histology confirmed the diagnosis of DNT. This report
shows that the smear preparation can be trustworthy for the
intraoperative diagnosis of DNTs, helping to determine the appropriate neurosurgical procedure and thus avoiding extensive and
unnecessary resections. Diagn. Cytopathol. 2002;26:92–94; DOI
10.1002/dc.10042 © 2002 Wiley-Liss, Inc.
Key Words: dysembrioplastic neuroepithelial tumor; smear preparation; magnetic resonance

The dysembrioplastic neuroepithelial tumor (DNT) was described in 1988 by Daumas-Duport et al.1 and incorporated
in the revised WHO classification in 19932 among the
category of neuronal and mixed neuronoglial tumors. The
clinical manifestations of DNT include partial and complexes seizures in a young population, refractory to the
1
Department of Pathology (Neuropathology), University of Paraná, Curitiba, PR, Brazil
2
Laboratory of Experimental Pathology, PUC-PR, Curitiba, PR, Brazil
3
Division of Neurosurgery, University of Paraná, Curitiba, PR, Brazil
*Correspondence to: Luiz F. Bleggi-Torres, M.D., Ph.D., M.I.A.C.,
Department of Pathology (Neuropathology), Hospital das Clı́nicas, UFPR,
Rua General Carneiro 181, 80060-900 Curitiba, PR, Brazil.
E-mail: lftorres@uol.com.br
Received 15 May 2001; Accepted 18 September 2001

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usual drug therapy, with no further underlying neurological
deficits. DNT is composed of small oligodendroglial-like
cells aligned along the side of an eosinophilic, occasionally
vascularized, core known as a specific glioneural element
and immersed in an abundant mucinous background, with a
somewhat microcystic appearance containing occasional
floating nerve cells. Cortical dysplasia might also be seen in
the adjacent cortex. The authors present a case report of
DNT with intraoperative diagnoses made by cytological
examination of a smear preparation.

Case Report
A 5-yr-old male presented in September 1999 with partial
seizures, with secondary generalization, for the preceding 3
yr. Physical examination showed a small reduction of the
cognitive functions, but no other neurological abnormalities. Magnetic resonance showed a superficial right temporal lobe lesion compatible with a low-grade glioma. The
patient underwent a craniotomy that demonstrated a welldelimited cortical temporal lobe lesion. Intraoperative diagnosis was made with 1 mm3 of tumor tissue that was
smeared between two glass slides and stained with 1%
aqueous Toluidin blue. The cytological observation showed
small, round, oligodendroglial-like cells arranged in lobules. Microcystic spaces containing large ganglion cells
floating in a fine fibrillary background were present. Foci of
perivascular distribution of tumor cells were also noted.
Blood vessels were thin-walled, with no endothelial proliferation (Figs. 1–3). Occasional areas with astrocytes were
also detected. No necrosis and no mitosis were noted. Following the smear cytology diagnosis of DNT, a complete
surgical resection was performed. The histological sections
confirmed the diagnosis (Figs. 4, 5). To date, the patient
remains well and free of seizures.
© 2002 WILEY-LISS, INC.

INTRAOPERATIVE SMEAR PREPARATION OF DNT

Fig. 1. Smear preparation of DNT, showing small round oligodendrogliallike cells in a fibrillary background with thin-walled blood vessels (Toluidine blue, ⫻100).

Fig. 2. High-power view of smear preparation of DNT, showing round
oligodendroglial-like cells arranged in clusters with occasional large floating nerve cells (arrow) immersed in a fibrillary background (Toluidine
blue, ⫻400).

Discussion
DNT is a superficial and intracortical lesion with multinodular architecture and a heterogeneous cell composition. The
term “dysembrioplastic neuroepithelial tumor” is proposed
for conditions that: 1) present with foci of cortical dysplasia
that imply its appearance during cortical development; 2)
are composed of different types of cells; 3) occur at a young
age; and 4) accompany bone abnormalities near the tumor.1,3,4 This is a benign, slow-growing lesion, surgically
curable with no need of further radio- or chemotherapy. For
this reason, early surgery can prevent other neurological
damage caused by persistent and chronic epilepsy, improving the quality of life and prognosis of those patients.1,3,5
The smear technique has been widely used in the diagnosis of brain tumors.6,7 The cytological presentation of
DNT in a smear preparation is pleomorphic, depending on
which component of the lesion is sampled. A mixture of

Fig. 3. High-power view of smear preparation of DNT. Arrow indicates
large floating nerve cell (Toluidine blue, ⫻400).

Fig. 4. Histological section of DNT, showing a microcystic tumor composed of cords of oligodendroglial-like cells delimiting small spaces that
contain floating nerve cells (hematoxylin-eosin, ⫻100).

ganglion cells, astrocytes, and cells resembling oligodendrocytes arranged in strains have been identified. DNT may
show areas of ganglion cells set in a fine fibrillary background, resembling a neuronal tumor or even relatively
unremarkable central nervous tissue. In other areas, oligodendroglial-like cells might predominate. These are frequently arranged in lobules closely related to thin-walled
blood vessels. Other areas might resemble a central neurocytoma with scattered ganglion cells. Mitotic figures are not
present. A characteristic feature of DNT is the cytological
variability of appearances in different areas of the smear
preparation, which confirms its variegated cellular
composition.
The differential diagnosis of DNT on cytological grounds
should be made with oligodendroglioma, low-grade astrocytoma, and ganglion-cell tumors. The smear preparation of
oligodendroglioma is composed of similar cells and might
form lobular structures. However, oligodendrogliomas are
uncommon in the temporal lobe of young patients and affect
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Ganglion-cell tumors can be confused with DNT by
showing a mixture of ganglionic and glial elements.3,4,8,9
However, these lesions are also slow-growing and normally
receive a neurosurgical treatment similar to that of DNT.
Knowledge of the entity, its clinical presentation, and its
peculiar CT scan and magnetic resonance-imaging appearance help the intraoperative diagnosis. Accurate diagnosis
of DNT and its distinction from ordinary gliomas have
important therapeutic implications such as establishing the
right margin at the surgery, and avoiding more aggressive
surgical decisions.1,3,5,8

References
Fig. 5. Histological section of DNT, showing nerve cell (arrow) immersed
in a population of oligodendroglial-like cells (hematoxylin-eosin, ⫻400).

mainly the deep frontal lobes, with frequent foci of calcification detected by CT scan. Nevertheless, the final distinction between these two entities may require histology.
Low-grade astrocytomas might present with an abundant
fibrillary matrix mimicking DNT. It is also important to
consider this differential diagnosis, since most of the temporal lobe gliomas, particularly low-grade astrocytomas,
might have unusual histological presentations with frequent
dysplastic features. An important cytological point that
might help this differential diagnosis is the presence of
neurons floating among the more primitive-looking oligodendroglial cells, which tend to be arranged in lobules or
clusters. Furthermore, surgical resection in astrocytic tumors, which are more infiltrative, tends to be more aggressive than in DNT, which is characteristically multinodular
and well-delineated from the surrounding brain tissue.

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